Colombian teachers and students march for improvements

Students wearing costumes face riot police as hundreds of teachers and students march during a protest in Medellin, Colombia, Sept. 5, 2012. Demonstrators were demanding better pay conditions and rejected the privatization of education.

William Fernando Martinez / AP

Protesters spit fire during a march by teachers and students in Bogota, Colombia, Sept. 5.

William Fernando Martinez / AP

A riot police officer, with a helmet stained by thrown paint, watches a march of teachers and students protesting a wide range of issues regarding the government's educational policies in Bogota, Colombia, Sept. 5.

Luis Eduardo Noriega / EPA

Hundreds of teachers and students march during a protest in Medellin, Colombia, Sept. 5.

Christian Escobar Mora / EPA

Teachers and students shout slogans during a protest against the Colombian National Education Ministry in Cali, Colombia, Sept. 5.